My club has also allowed the use of pistol caliber carbines for three gun matches since no one could find .223/5.56 for a while there.
Two of these carbines both 9mm have been used and they performed well enough but they are a little ammo sensitive especially with light 115gr bullets and hollow points. 124gr Nato and CCI 124gr Lawman ran well in the guns seen.
I searched and found nothing for user groups of JR carbines.
If you have not purchased the JR yet research the Ruger PC9 carbine and check the used marked for these gun. These PC9 carbines are built like tanks, have excellent sights and are very accurate. Plus they will shoot any weight ammo without issue and magazines are easy to find.
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